Heretofore, in regard to a multi-cylinder engine mountable on an automotive vehicle or the like, developments of an exhaust apparatus intended to improve torque performance have been promoted.
For example, the following Patent Document 1 discloses a technique in which exhaust ducts of cylinders which are non-successive in terms of exhaust order are bundled and merged together as a tapered exhaust pipe, and an ejector effect is imparted to a throat of the merged portion to thereby prevent exhaust interference between the cylinders.    Patent Document 1: Japanese Patent Application Laid-open No. H04-036023